UNRESTRICTED/ILLIMITÉ
NDE Inspections of the NRU
Calandria Vessel
Part 1: NRU and ET Inspections
3rd International CANDU In-Service
Inspection and NDT in Canada
2010 June 14-17
Presenters: R. Lakhan & R.H. Lumsden
Overview
• First Presentation
–Overview of NRU
–Low-Resolution ET for Corrosion Assessment
–Hi-Resolution ET Scanning of Inside Vessel Surface
–ET Marking of Repair Locations
–ET Repair Inspection Technique
• Second Presentation
–Mk. I and II Inspection Tools
–UT Inspection Techniques
–Summary
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Inspection Progression
• Heavy water leak discovered in May 2009
• Visual inspection in the annulus confirmed the leak
• Leak located 10 meters below the reactor deck
• Above bottom flange, which is welded to the vessel wall
• Access through 120 mm diameter reactor positions
• Reactor shutdown, de-fuelled, and partially drained in mid. June
• Seven inspection campaigns required to determine the vessel
condition and provide information for a repair strategy
• Combination of ET and UT
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May
Combined
ET-UT
High
Resolution
ET
PA-UT
Wall
Thickness
UT
Vertical
Strips
UT
Below
Weld
ET
Marking
ET/UT
Repair
June July Aug. Sept. Oct. Nov. Dec.
Leak
Detected
What is NRU?
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STANDBY MOTOR D.C.
HEAVY WATER PUMP
PUMP MOTOR A.C.
FUELING
MACHINE
NEUTRON BEAM HOLES
BOTTOM RING
THERMAL SHIELDS
FUEL RODS
SHELDING BLOCKS
CONCRETE SHELDING
DECK PLATE
THERMAL SHIELDS
ALUMINUM TANK
NEUTRON BEAM HOLES
WARM HEAVY WATER
HEAT EXCHANGER
PROCESS WATER
COOLED HEAVY WATER
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Plan View of the NRU Reactor Vessel
Adjuster Rod
Isotope Production Sites
Fuel Rods
Blocked Sites
Control Rods
Dummy Rods
Flux Detectors
Vacant Sites
Experimental Irradiation Sites
Experimental Test Loops
Vessel Overview
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Re-entrant
Cans
Through
Tubes3.5 m
Top-of-Reactor (TOR)
Reactor
Vessel
Leak
Site
10 m
Annulus
Material: Aluminum 5052, 8 mm Thick
Leak of the NRU Calandria Vessel
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Heat Baffle
Lower Weld
Annulus
Leak Site
Inner Wall
Water
ReflectorVessel(D20)
Tapered Flange
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ET Probe Design Approach
• All ET probes developed and manufactured in-house
• Transmit-Receive type probes used in all designs
• FEM Modelling used to design probes, optimize parameters,
and simulate signals of possible flaw types
• Two coil configurations used: G3 and G4
G4 mode
Scan
Direction
G3 mode
Scan
Direction
+ +T R
++
R
T
Combined ET-UT
• Vessel partially drained of heavy water
• Measurement of wall thickness and detection and sizing of corrosion
• Combined 3 T/R ET array and conventional UT head
• UT – Far Surface/ET – Near Surface
• ET Large Diameter Coils with Large Spacing
• ET Maximize Penetration (6-7 mm)
• ET monitored Lift-off for data quality (1 mm or less)
• UT probes from AFCIS
• UT 10 MHz, 9.5 mm Diameter
• Minimum thickness UT can reliably measure - 3 mm
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May
Combined
ET-UT
High
Resolution
ET
PA-UT
Wall
Thickness
UT
Vertical
Strips
UT
Below
Weld
ET
Marking
ET/UT
Repair
June July Aug. Sept. Oct. Nov. Dec.
Leak
Detected
UT
ET
Combined ET-UT
• Two methods chosen due to Aluminum Oxide/
Hydroxide layer on vessel wall
• Data acquisition and preliminary data analysis on TOR
• Very complementary ET confirming UT and vice versa
• Camera on separate tool inside the vessel for
guidance
• Limited visibility due to water in vessel and turbidity
• Required very close liaison with procurement,
manufacturing, designers, transportation, inspectors,
quality assurance, and operations.
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May
Combined
ET-UT
High
Resolution
ET
PA-UT
Wall
Thickness
UT
Vertical
Strips
UT
Below
Weld
ET
Marking
ET/UT
Repair
June July Aug. Sept. Oct. Nov. Dec.
Leak
Detected
Corrosion No Corrosion
ET Probe and Corrosion Signal
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• Frequencies: 500 Hz, 2000 Hz, 4000 Hz, 10000 Hz
• Sizing curves developed for sizing wall thickness
Ch. 1 Ch. 2 Ch. 3
Ch. 1
Ch.2
Ch. 3
44 mm
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High Resolution ET Probe
• Re-inspects areas with external corrosion
• Inspection of near surface
• Accurately locate the leak site
• Frequencies: 2500, 5000, 7500, 15000 Hz
• Measuring wall thickness 4 mm or less
R01 R02 R03
R04 R05 R06 R07
T01 T02 T03
T05 T06 T07 T08
T04
Scan
Direction
56 mm
May
Combined
ET-UT
High
Resolution
ET
PA-UT
Wall
Thickness
UT
Vertical
Strips
UT
Below
Weld
ET
Marking
ET/UT
Repair
June July Aug. Sept. Oct. Nov. Dec.
Leak
Detected
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Hi-Resolution ET Signal of Leak Site
Leak Site
Comparison of Results:
Wall Thickness Map
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May
Combined
ET-UT
High
Resolution
ET
PA-UT
Wall
Thickness
UT
Vertical
Strips
UT
Below
Weld
ET
Marking
ET/UT
Repair
June July Aug. Sept. Oct. Nov. Dec.
Leak
Detected
High Resolution ETConventional UT
Leak Site
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ET Marking Phase
• Inspect corroded areas and accurately mark flaw locations
• Complete 360 ET scanning of near surface
• Scanning direction: horizontal
• Frequencies: 2500, 5000, 7500, 15000 Hz
• Sizing curves for wall thickness 4 mm or less
• Using a mixture of amplitude and phase curves for sizing
• High frequency phase curves best for localized flaws
• 32-Coil Transmit-Receive Array Probe
May
Combined
ET-UT
High
Resolution
ET
PA-UT
Wall
Thickness
UT
Vertical
Strips
UT
Below
Weld
ET
Marking
ET/UT
Repair
June July Aug. Sept. Oct. Nov. Dec.
Leak
Detected
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32-Coil High Resolution Array Probe
G3 and G4 modes operate separately by changing adapters
Scan
Direction
1-R7
2-T8
3-R6
4-T7
5-R4
6-T6
7-R3
8-T5
9-R7
10-T8
11-R6
12-T7
13-R5
14-T6
15-R4
16-T5
1-T4
2-R8
3-T3
4-R5
5-T2
6-R2
7-T1
8-R1
9-T4
10-R3
11-T3
12-R2
13-T2
14-R1
15-T1
1R-R8
CFN02
CFN04
CFN06
CFN08
CFN10
CFN12
CFN14
CFN16
CFN18
CFN20
CFN22
CFN24
CFN26
CFN28
CFN30CFP29
CFP27
CFP25
CFP23
CFP21
CFP19
CFP17
CFP15
CFP13
CFP11
CFP09
CFP07
CFP05
CFP03
CFP01
1-T16
2-T15
3-T14
4-T13
5-T12
6-T11
7-T10
8-T9
9-T8
10-T7
11-T6
12-T5
13-T4
14-T3
15-T2
16-T1
1-R16
2-R15
3-R14
4-R13
5-R12
6-R11
7-R10
8-R9
9-R8
10-R7
11-R6
12-R5
13-R4
14-R3
15-R2
16-R1
G3 mode G4 mode
120 m
m
“The Brick”
Inspection Planning
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Position Verification
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LASERBaffle
Bolt Resolver: Horizontal Position
Encoder: Vertical Position
• Inspect region in a single pass
• Position probe and hold at the deepest flaw location
• Deploy tool to mark location
• Mark “wings” for visual clarity
• Marks used to position the welding electrode
Elevation Above
Taper Transition
Taper Transition
Mark Directly
Above Tmin▬ ● ▬
Marking of Repair Locations
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Distance to Tmin
Marking In Vessel
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Tool Arm
Nuclear
Grade Marker
Mark
Pneumatic Cylinder
Post Repair ET Probes
• ET for detection of surface-breaking flaws in repair
• Used as an alternative to liquid penetrant testing
• Based on X-Probe coil layout and operation
• Simultaneous operation of G3 and G4 modes
• Provides detectability to linear flaws in the transverse and
longitudinal directions, and volumetric flaws
• Smaller coils spacing to achieve higher resolution
• Higher frequencies to inspect surface only
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May
Combined
ET-UT
High
Resolution
ET
PA-UT
Wall
Thickness
UT
Vertical
Strips
UT
Below
Weld
ET
Marking
ET/UT
Repair
June July Aug. Sept. Oct. Nov. Dec.
Leak
Detected
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ET Post Repair Probes
• Frequencies: 7.5, 15, 25, 50 kHz
• External multiplexer located on the reactor deck
• Two probe variants: horizontal and vertical orientation
depending on weld bead direction
Scan
Direction
Scan
Direction
48 mm
Example Signals – EDM Notch Plate
• Signals obtained on Flat Plate
• EDM notches
–1.5, 2, 3 and 5 mm deep
–1.5, 3, and 10 mm long
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ET Performance Demonstration Samples
• Weld overlay test sample
• EDM notches 0.5 to 3 mm deep, 3 to10 mm long
• All notches 0.125 mm wide
• Flaws on crown, in valleys and in heat affected zones
• ET technique for detecting flaws in crown and valleys
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Example Signal – Qualification Sample
Signals obtained with Post Repair ET Probe
Fatigue Crack Samples
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• Three fatigue crack specimens manufactured
• Only detectable with florescent PT, ET and UT
• Each sample contained 14 cracks
• Two specimens destructively analysed
• 6 to 16 mm long
• 2 to 5 mm deep
Example Data – Mock-up Sample
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G4 Mode
G3 Modewww.nrucanada.ca
PROTECTED - SENSITIVE / PROTÉGÉ - DÉLICAT 28UNRESTRICTED/ILLIMITÉ